This invention relates in general to a transfer assembly for use in a reproduction apparatus, and more specifically to a mounting mechanism for a roller transfer assembly that accurately positions the roller transfer assembly in operative relation with a dielectric member of a reproduction apparatus with an anti-castor gimbal locking coupling.
In reproduction apparatuses, such as copier/duplicators or printers, a latent image charge pattern is formed on a uniformly charged dielectric member. Pigmented marking particles are attracted to the latent image charge pattern to develop the latent image on the dielectric member. The dielectric member is then brought into contact with a receiver member, and an electric field is applied to transfer the developed image to the receiver member from the dielectric member. After transfer, the receiver member bearing the transferred image is transported away from the dielectric member and the image is fixed to the receiver member by heat or pressure or both to form a permanent reproduction thereon.
The electric field is generated by ion emission from a corona charger onto the receiver member while in contact with the dielectric member, or by an electrically biased roller that urges the receiver member against the dielectric member. A roller transfer apparatus has certain advantages over a corona transfer apparatus. The roller transfer apparatus substantially eliminates defects in the transferred image due to paper cockle or marking particle flakes. Those defects occur when a pressure roller urges the receiver member against the dielectric member. However, roller transfer apparatuses are more complex than corona transfer apparatus. Roller apparatuses require cleaning due to their tendency to pick up marking particles from the dielectric member and undesirably deposit such particles on the back side of the receiver member. Further, the roller transfer apparatus, including the cleaning assemblies must be constructed so as not to interfere with ready clearance of any jammed receiver members. An example of a selectively positionable roller transfer apparatus constructed to include a cleaning mechanism is shown in U.S. Pat. No. 5,101,238 (issued 1992, in the names of Creveling, et al).
While roller transfer apparatuses are generally effective in transferring images comprising particles, they tend to impose undesirable tracking effects on the dielectric member, particularly when the dielectric member is in the form of an elongated web. U.S. Pat. No, 5,491,544 (issued Feb. 13, 1996, in the names of Kenin et al) shows a transfer assembly, of compact configuration, for a reproduction apparatus. The transfer assembly includes a transfer roller for transferring of a pigmented marking particle image from an elongated web dielectric member to a receiver member. A mechanism for mounting the roller transfer assembly includes a support for the transfer assembly connected to the transfer assembly such that the transfer roller of the transfer assembly is castored and gimbaled, However, this mechanism relies on the weight of the transfer assembly to establish the proper engagement with an unsupported span of the dielectric member. The weight of the transfer assembly can be controlled to position the transfer assembly as shown and described in U.S. Pat. No. 6,097,913, whose entire disclosure is hereby incorporated by reference. However, even with the improvement made by the latter invention, the transfer assembly may castor about its gimbal axis when the gimbal lock is tightened.
This invention is directed to a mechanism for mounting a transfer assembly in a reproduction apparatus and locking the transfer assembly at a chosen position about the gimbal axis without castoring the transfer assembly. The reproduction apparatus has a first or mounting bracket that is fixed or part of the machine housing. A second or transfer bracket holds and supports the transfer assembly. The transfer assembly includes an electrically biased transfer roller for transferring pigmented marking particle images from a dielectric member to receiver members. The transfer assembly is castored and gimbaled. An anti-castor coupling locks the mounting bracket to the transfer assembly. The anti-castor coupling is a third bracket with a pair of arms oriented at 90 degrees or more with respect to each other. The upper arm of the third bracket has a threaded opening for receiving a gimbal locking screw. The lower arm has two or more slots. Lock screws pass through the slots and engage threaded openings in the second or transfer bracket. The third bracket is slid to bring the upper arm of the third bracket into contact with the first bracket. Then the third bracket is fixedly secured to the second bracket. The transfer assembly is moved about its gimbal axis to its desired position. Once the transfer assembly is in its desired position, the gimbal lock is firmly tightened to lock the gimbal axis without castoring the transfer assembly. The third bracket keeps a gap between the transfer bracket and the mounting bracket. The third or anti-castoring bracket or at least its upper arm that connects it to the mounting bracket is relatively thin compared to the mounting bracket. The physical formation of the third or anti-castoring bracket renders it less stiff or more deformable than the mounting bracket. When the gimbal lock screw is tightened to draw the coupling bracket to the bracket, the coupling bracket deforms and thus absorbs the castoring torque generated by the gimbal lock screw.
The invention overcomes the disadvantages of the prior art. It adds a third bracket, but the cost of the added bracket is small compared to the improved performance of the transfer assembly. With the added third bracket the transfer assembly remains in its desired position after the gimbal lock is set. The invention will be become more apparent in the detailed description below when read in conjunction with the drawings.